Battery operated devices find diverse applications ranging from small and simple children's toys to sophisticated laptop computers and large electric powered vehicles. Batteries are also used in medical devices, such as manual, automatic or semiautomatic defibrillators. Defibrillators and other medical devices may be external or implanted in the body. Automatic and semiautomatic external defibrillators are referred to by the abbreviation “AED” or “AEDs”. External defibrillators are described in U.S. Pat. No. 5,803,927 to Cameron et al., and in European Patent Application EP 0 757 912 A2 to Olson et al. Battery arrangements for use in AEDs and other portable equipment are described in U.S. Pat. No. 5,314,451 to Mulier, in U.S. Pat. No. 6,441,582 to Powers, in U.S. Pat. No. 6,268,709 to Lee et al., in U.S. Pat. No. 5,741,305 to Vincent et al., in U.S. Pat. No. 6,157,531 to Breyen et al, in U.S. patent application Publication No. U.S. 2002/0138103 to Mulhauser, in European Patent Application EP 1 093 829 A1 to Muffoletto et al., and in International (PCT) Patent Application No. WO 96/22811 (PCT/US96/00763) to Kroll et al.
The battery of a medical device is typically provided in a module. The module is typically a collection of battery cells. Each battery cell is provided in a housing, out of which emerge two electrical contacts. One of the contacts is coupled to an anode plate and the other to a cathode plate inside the battery cell. An electrolyte between the anode and the cathode plates permits them to interact chemically. The anode and the cathode have different tendencies to gain or lose electrons. This difference in electron affinity is harnessed in a chemical reaction to accomplish useful work. The amount of work or energy available depends on the magnitude of the electron affinity difference and quantity of the anode and cathode materials available for the chemical reaction. The difference in affinity is a function of the battery chemistry of the battery cell.
FIG. 1 shows typical prior art battery module 10 with terminals 12, 13 (FIG. 1 is a reproduction of FIG. 2B of U.S. Pat. No. 6,441,582 B1). Module 10 has M branches with N cells 14 in each branch. The total output voltage VT of module 10 appearing between terminals 12, 13 is N*V where V is the voltage of each cell 14. There is a current blocking device 16 connected in series with each of the M parallel strings to prevent a reverse current or charging condition from another parallel string in battery module 10. Current blocking device 16 can be a diode with the anode connected to the positive side of the string being protected and the cathode connected to positive output 13.
The prior art suffers from a number of disadvantages and limitations. For example, with the arrangement shown in FIG. 1, all cells in module 10 are coupled together. This creates design constraints, especially when it is desired to minimize degradation or failure of the module due to failure of one or more of individual cells 14. Another limitation of the prior art is that the input voltage needed to charge the battery array must generally be equal or greater than the output or operating voltage of the battery array. This creates significant difficulties when the application requires large outdoor or operating voltages.
Accordingly, it is desirable to provide an improved means and method for portable power supplies for medical devices, especially battery operated medical devices such as defibrillators. In addition, it is desirable to provide an arrangement wherein the charging voltage and operating voltage need not be in fixed relationship, and especially where the charging voltage can be less than the operating or output voltage. Still further, it is desirable that the battery arrangement be programmable and reconfigurable with respect to the interconnection of individual cells. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.